This study will estimate the prevalence of Senile Dementia of the Alzheimer's Type (SDAT) among men and women 65 years of age and older, using standard, comparable methodology. Test instruments will also be validated in the field, to establish whether differences in occurrence and identified risk factors exist in the burden of SDAT among African Americans, Cuban Americans and white non-Hispanics. Medical and work histories, demographics, and measures of diet and cardiovascular system parameters will be collected to identify other variables cross sectionally associated with SDAT and to determine whether differences exist between the three ethnic groups among the cognitively normal. Follow-up analyses will also be done on a sample of participants testing positive or negative for specified screening cognitive tests to establish the sensitivity and specificity for detection of SDAT in a mixed cultural U.S. population. Possible cases will be first identified among populations in selected census tracts in Dade County Florida using screening instruments for cognitive impairment. Defined cases of possible dementia will be referred to one of two Memory Disorder Clinics for a standard battery of tests to diagnose SDAT and other dementias. The number of probable cases will then be used to calculate prevalence of the disease among the three ethnic groups. Approximately four thousand participants will be examined with equal numbers in each ethnic group and equal numbers of men and women. The cognitively normal evaluated population will be available for future longitudinal studies of risk factors and incidence of SDAT.